Ioc Breakthrough To Lift Crude Distillate Bottomline
In a major technological breakthrough, the research and development centre of the Indian Oil Corporation (IOC) has devised a method to improve middle distillate yield by over two per cent in weight through selective ugrading of bottoms.
The one-year plant trial of the technology on a distillate-mode fluid catalytic cracking (FCC) unit with an annual feed-processing capacity of one million tonnes, has resulted in net economic benefits of $1.5 million.
The researchers used a bottom-cracking additive (BCA) in the distillate-mode fluid catalytic cracking unit. The BCA is a large-pore, non-crystalline, silica-alumina matrix with sufficient acidity to precrack larger molecules.
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Fluid catalytic cracking is a major secondary conversion process in Indian refineries.
Conversion of bottom fractions (materials having a boiling point higher than 370 degree centigrade) and maximisation of middle distillate (diesel) yield are two major objectives of Indian FCC units. Distillate-mode FCC operations lead to higher amounts of unconverted bottoms than that of gasoline-mode FCC units.
Indian distillate-mode fluid catalytic cracking units are generally equipped with a partial combustion regenerator. The units are usually operated at low reaction temperatures and have low catalyst-to-oil ratios.
The process results in a considerable amount of unconverted bottoms, part of which is recycled back to the riser reactor for further cracking. The recycling is done within the limits of allowable regenerator temperature and the air blower capacity, but the unconverted bottoms yield is still much more than that of the gasoline-mode operations.
In the experiment conducted by IOC researchers, an ReY-type catalyst was used as host catalyst. Both the additive and catalyst were separately steamed at 788 degrees Centigrade for three hours in an atmosphere of 100 per cent steam. The performance of the BCA was evaluated at different concentrations with the host catalyst in a laboratory fixed bed micro-reactor, which simulated a distillate-mode FCC operation.
The pre-treated catalyst and additive were mixed together at different concentrations for the evaluation. The product selectivities with BCA additive were established from the simulated data taken at different reaction severity levels in the micro-reactor. The results obtained through this experiment were fed into an in-house developed FCC simulator for the performance prediction of the additive at equal coke levels like those observed in the heat balanced commercial FCC unit.
The success of the new process has encouraged IOC to use the BCA in its Mathura refinery.
It has been found that the BCA minimises bottoms while processing heavier vacuum gas oils (VGOs), particularly those containing higher basic nitrogen and aromatics.